When producing a folded document, it is generally preferable first to form a crease in the document. This produces a neat fold-line and it reduces the risk of cracking or tearing when the document is folded.
Conventionally, documents have been creased on a platen press or using a hand-operated machine with a rotating scoring wheel, which rolls across the surface of the document to produce the crease. However, it has been found that this system can lead to cracking of the printed surface, particularly with documents printed using modern ink or toner-based digital printing systems, or on easily damaged materials.
Further, existing creasing machines are either very slow (in the case of hand-operated machines) and therefore unsuitable for anything but very small production runs, or require the manufacture of a custom creasing die (in the case of platen presses), and are suitable therefore only for very large production runs.
One type of known machine uses a pair of creasing elements, wherein one of the creasing elements is arrange to move vertically towards the other to stamp sheets of paper located between the elements to form creases therein. The machine includes a paper feed system that positions the paper sheet between the creasing elements such that its movement is stopped for the creasing operation. Thus the paper is static when the creasing operation takes place and therefore the machine has a limited throughput. The paper has to be static in order for the creases to be formed otherwise the paper is torn and/or is crumpled.
Another known type of creasing machine includes a pair of rotary creasing blades having creasing formations formed therein. The blades rotate continuously in a synchronous manner about fixed axes and are arranged to receive sheets of paper in a nip formed between the blades. While this type of machine has been successful for the applications for which it was designed, it is not suitable for all creasing applications required by the creasing industry.